To achieve increased effectiveness and improved reliability of the refractory linings of metallurgical vessels in steelworks, it is necessary to obtain as much information as possible about the wear of the linings during use (the so-called “campaign”) of the vessels.
In this context, precise knowledge of the thickness of the refractory lining—also called “remaining refractory thickness”—is especially important, since it permits effective utilization of the refractory lining up to the wear limit without an increased risk of blowout of the metallic jacket of the metallurgical vessel.
Consequently, efforts have been underway for quite some time to develop measurement methods that permit precise measurement of the metallurgical vessels. For reasons of time and cost, these methods should not require the vessel to be cooled; instead it should be possible to carry them out in a vessel that is still hot. For this reason, and also due to the inaccessibility of many metallurgical vessels, contacting measurement is inherently out of the question.
A non-contacting measurement method for determining lining wear by the company Ferrotron Elektronik GmbH, of Moers, has thus become known wherein the inner surface of the vessel is scanned by a laser beam and the surface structure of the refractory lining can be imaged by distance and angle measurements. The remaining refractory thickness can be determined by comparison to the reference measurement performed on the metallurgical vessel prior to its campaign.
A prerequisite for wear measurement of the refractory lining of metallurgical vessels by noncontacting methods is determining the position of the object coordinate system of the metallurgical vessel to be measured relative to the device coordinate system of the measurement equipment used for the measurement so that the measurement equipment and the vessel can be brought into the same coordinate system through coordinate transformation.
Known from U.S. Pat. No. 4,025,192, for example, is an optical method for measuring the lining of a metallurgical vessel for the purpose of reconstructing the object coordinate system on which is based a reference measurement of the vessel prior to the campaign with a subsequent wear measurement. In this method, the coordinates of three reference points about the mouth of the metallurgical vessel are, in a first step, determined using a theodolite by means of angle and distance measurements, and the lining is likewise measured by means of angle and distance measurements of individual points.
After the vessel has been used, the reference points and the lining are measured again and the current position of the object coordinate system relative to the position of the device coordinate system is determined by comparing the coordinates of the first reference points measured with the most recently measured coordinates, and a change in position is accounted for in the analysis of the measurement points for the lining. The electromagnetic radiation emitted by the measurement device is manually aimed at the reference points with the aid of a telescopic sight.
Although it has been demonstrated that the position and orientation of the vessel can be determined and also reconstructed before a subsequent wear measurement using this method, the method has the disadvantages that it is cumbersome because it is performed manually, and it has a significant probability of error.
For this reason, and also because automation of the method seemed especially difficult, a process described in DE 196 14 564 A1 was developed wherein a reference mark system on the jacket surface of the vessel is recorded by a camera unit during the reference measurement and before the subsequent wear measurement. The differences between the vessel's position in the reference situation and the measurement situation are deduced from the difference in the position and geometric shape of the reference mark system. While this method does in principle provide automation, it has the disadvantage that the achievable precision of measurement is limited both by the necessarily small size of the reference mark system and the resultant small displacement of individual points of the reference mark system when the vessel's position is changed, and by the merely two-dimensional position determination of the reference points. Moreover, this method requires a separate, advance determination of the position of the vessel relative to the measurement device, which increases the amount of time needed for performing the wear measurement.
DE 198 08 462 A1 discloses a method in which three reference points provided on the metallurgical vessel are first measured by an optical identification unit, but then, after automatic alignment of the measurement equipment with each of the reference points in sequence, the precise positions of the reference points in space are determined by means of the actual measurement equipment, which can include a LASER distance measuring device.
While this method has improved precision of measurement over that of DE 196 14 564 A1 because three-dimensional information is obtained by using the actual measurement equipment to determine the position of the reference points, it nevertheless has the disadvantage of requiring an advance reference measurement using the optical identification unit.
Another method for determining the position of a metallurgical vessel is known from U.S. Pat. No. 5,212,738. Here, the vessel is measured from two different positions, and the position is determined by superposition of the images.
This method has the drawback that the positions must be known precisely relative to one another, which increases the measurement effort.